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Question 1
Collision theory is a principle of chemistry used to predict the rate of a reaction. |
a) | State the two conditions in collision theory that must be met for a collision to be successful.
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b) | Define the term activation energy.
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c) | State two factors that affect the rate of a reaction.
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Question 2
The diagram below shows a Boltzmann distribution curve for a sample of gas molecules. |
a) | What does the area under the curve represent?
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b) | Which letter represents the mean energy of the molecules? A B C D
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c) | What does the letter D represent?
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d) | Why does the curve begin at the origin?
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Question 3
This question is about catalysts and the role they play in reactions. |
a) | State the meaning of the term catalyst.
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b) | Explain in general terms how a catalyst works.
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c) | The diagram below shows the Boltzmann distribution for a sample of ammonia molecules. Ammonia can undergo a decomposition reaction into its elements. Label the diagram to show the position of the activation energy when a catalyst is used in the decomposition.
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d) | Explain how a catalyst increases the rate of a reaction. Refer to the Boltzmann distribution in your answer.
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Question 4
The rate of a reaction is affected by a number of different factors including temperature. |
a) | Explain how an increase in temperature affects the rate of reaction, referring to ideas about collision theory in your answer.
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b) | The diagram below shows the Boltzmann distribution for a sample of gas molecules. Sketch a second curve on the diagram to show the distribution at a higher temperature.
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c) | Explain with reference to both curves how a small change in temperature can lead to a large increase in the rate of reaction.
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Question 5
The diagram below shows two Boltzmann distribution curves for a sample of gas molecules at two different temperatures. |
a) | Which letter represents the most probable energy at the lower temperature?
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b) | Which letter represents the mean energy of the molecules at the higher temperature?
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c) | Give one reason why most collisions in the gas phase do not result in a successful collision.
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Question 6
Hydrogen peroxide solution undergoes a decomposition reaction to form oxygen gas. |
a) | Explain how increasing the concentration of hydrogen peroxide affects the rate of reaction.
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b) | Explain how adding a catalyst would increase the rate of the reaction.
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c) | The diagram below shows the Boltzmann distribution for a sample of hydrogen peroxide molecules. Add a second curve on the axes to show the distribution at a lower temperature.
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Question 7
Hydrogen gas can be reacted with oxygen to produce water. |
a) | Explain how an increase in pressure would affect the rate of reaction.
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b) | The diagram below shows the Boltzmann distribution curve for a sample of hydrogen gas molecules at a specific temperature. Mark the position of the most probable energy of the hydrogen molecules.
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c) | The diagram below shows the same distribution. Sketch a new curve to show the distribution at a lower temperature.
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Question 8
This question is about catalysts and how they can affect the rate of a reaction |
a) | Use the idea of activation energy to explain why a catalyst speeds up a reaction.
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b) | Draw a labelled Boltzmann distribution curve on the axes below to illustrate the effect of adding a catalyst to a reaction.
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Question 9
Collision theory is used to predict the rate of a reaction. |
a) | Explain what must happen for a reaction to occur between molecules of two different gases.
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b) | The diagram below shows the Boltzmann distribution for a sample of gas molecules. Sketch a second curve on the diagram to show the distribution at a higher temperature.
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c) | State the effect, if any, of a catalyst on the shape of these distributions.
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d) | Other than by increasing the temperature or by using a catalyst, explain another way in which the rate of a reaction could be increased.
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Question 10
The temperature of a reaction can be changed to influence the rate of a reaction. |
a) | Other than by increasing the temperature, state one way in which the collision frequency between particles in a gas could be increased.
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b) | Explain why a small increase in temperature can lead to a large increase in the rate of a reaction.
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c) | Sodium thiosulfate reacts slowly with hydrochloric acid. Explain why, at constant temperature, the rate doubles if the concentration of hydrochloric acid is doubled.
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